Orbital abrading or polishing tools have been available for many years. Examples of such tools are presented in U.S. Pat. Nos. 4,592,170; 4,660,329; 4,671,019; 4,839,995; 4,986,036; 5,445,558; 5,597,348; and 6,485,360 each to Hutchins and all of which are incorporated by reference in their entirety into the present disclosure.
Orbital sanding tools of the prior art have, in some instances, been shaped to be held by a user in manipulating the tool and moving it along a horizontal work surface to sand the work surface. Such sanders often utilize a head which carries a sheet of sandpaper and is driven rotationally by a compressed air powered motor. The motor is usually contained within a rather heavy body structure.
Typically, the head is mounted to a spindle which in turn is mounted eccentrically relative to the vertical axis of the motor so that the head orbits about the vertical axis. It is often desirable to be able to quickly and easily remove the head from the drive portion of the sander in order to enable interchangeable use of any of several heads of different sizes and shapes with the same drive unit. A drive unit and a set of different heads can then perform, in effect, as a number of different tools. In the prior art, replacing the head has been relatively difficult because tools have typically been required for unscrewing the head from the drive portion of the orbital sander.
Previously developed portable orbital sanders have utilized a flexible shroud to provide access for insertion of a tool between the head and the housing to lock the spindle so that the head can be unscrewed manually from it. Located within the shroud and just above the spindle is a rotating counterweight used to counterbalance the eccentrically mounted spindle and head. This arrangement has several disadvantages, however. First, the flexible shroud can be pressed inwardly by an operator's fingers until it contacts the rotating counterweight. This causes wear to the sander in addition to unwanted vibrations. Also, debris can enter the space between the shroud and the head, and thus clog the inner workings of the sander, if the flexible shroud becomes distorted. Further, there is a risk that the fingers of the operator might enter the space, causing injury to the user.
Another structure for locking the spindle of an orbital tool to facilitate replacement of an abrading or polishing head is disclosed in U.S. Pat. No. 6,485,360. The structure of the '360 patent has a push button actuable to engage a notch in the circumference of the spindle in a locking relationship. Such a structure is difficult to incorporate in a tool with a small spindle diameter, however.